The field of the invention is that of thermally responsive electrical switches, particularly those adapted for use with electronic controls and the like in automotive applications.
Thermally responsive snap-acting thermostat metal discs have been used in a variety of automotive applications for performing various control functions in response to selected changes in engine temperature. It is now proposed that various electronic control means utilizing microprocessors and the like be provided for regulating operation of automotive engines to achieve improved fuel economies and efficiencies. For this purpose, it has been proposed that sensor means be arranged to provide inputs to the control means representative of various engine operating parameters such as engine temperature. For example, it has been proposed that such electronic controls be used with engine temperature sensing means for regulating fast idle means on the engine so that the fast idle means would be actuated below a first temperature during engine warm-up, would be deactuated above that first temperature during normal running of the engine, and would be reactuated if the engine were heated above a second temperature during extended standing or idling operation of the engine on a warm day, thereby to prevent vapor lock and to improve engine cooling. In this regard, it would be desirable if the temperature sensing means used with such electronic controls were adapted to provide digital signals corresponding to specific selected engine temperature conditions, thereby to facilitate signalprocessing by the electronic control. It would also be desirable if the engine temperature sensing means were compactly and inexpensively adapted to provide digital signals representative of two different engine temperatures, thereby to facilitate two-stage regulation of fast idle means and the like on the engine. It would also be desirable if such engine temperature sensing means were easily varied to sense different temperature levels and were easily adapted to be connected to electrical controls made by or for different automotive manufacturers while still being adapted for low cost mass production, whereby the sensing means could find wide application even in less expensive engine control systems.
It is an object of this invention to provide a novel and improved thermally responsive electrical switch; to provide such a switch which is adapted to respond to two different temperatures to provide digital signals representative of the temperature levels; to provide such a switch having a construction such that it is readily varied to operate at different temperatures and is easily modified to facilitate connection to controls made by different manufacturers but is also adapted for convenient and economical manufacture to achieve wide spread, low cost application. It is also an object of this invention to provide a novel and improved two-stage fast idle control system for an automotive engine using such thermally responsive electrical switch.